ETH improves its environmental footprint

The decision has been made: the Swiss energy system will undergo a thorough renovation by 2050, with a shift away from nuclear energy towards the use of renewable energy sources. The timescale for reducing CO2 emissions and the use of fossil fuels is shorter still, with the target being set at a decrease of at least 20 percent by 2020 compared to the levels recorded in 1990. To create a sustainable society, energy needs to be saved anywhere it can – including in the mobility sector, in industrial and service enterprises, in towns and cities and, above all, in the building sector.

According to the European Commission, building construction and maintenance – including heating, air conditioning, lighting and electrical equipment – accounts for 40 percent of energy consumption within the EU. The latest generation of architects therefore has a responsibility to help find a long-term solution to this energy problem.

A trial run for new building systems

One man who cares very much about forward-looking building systems is Hansjürg Leibundgut, a professor at the Institute of Technology in Architecture. He has designed the “LowEx” building system, which makes it possible to supply energy to new builds or renovated buildings while keeping emissions to a minimum with the help of geothermal probes, hybrid collectors and heat pumps. The insights gained into this specialist area to date have now been put to the test in a kind of trial run – as part of the renovation of the former central building of the Department of Physics on the Hönggerberg campus.

This office block was built on the verdant hilltop site during the first phase of the campus’ construction in the 1960s. Known by the acronym “HPZ”, it has now been completely revamped over the course of a comprehensive redevelopment programme as part of the ETH Zurich’s strategy for improving its environmental footprint. The building’s poor insulation ratings and high levels of heat loss in the winter did not satisfy modern requirements for low primary energy consumption and minimal environmental impact. “The original, conventional redevelopment concept was based on a thorough reconstruction”, says Philippe Goffin, a doctoral student under the Chair of Building Systems, outlining the history behind the building’s restoration.

This would have involved stripping the building right back to its basic structure and then adding a new façade, a new roof and new technical installations. “That would have been a great shame, as it would have meant destroying the high-quality and aesthetically superb aluminium façade developed by Albert Heinrich Steiner.”

Steiner, a Zurich-based architect, urban planner of long standing and professor of architecture and urban design at ETH Zurich, drew up the plans for the complete development of the university’s Hönggerberg campus in the late 1950s and oversaw the construction of the first buildings, including the HPZ building. To protect and preserve the building’s distinctive façade, to avoid unnecessarily wasting large quantities of high-quality material and, at the same time, to reduce grey emissions during the construction process, a group of researchers led by Professor Leibundgut developed an alternative renovation strategy. They proposed retaining the original façade everywhere but at ground floor level, while simply replacing the window glazing and reinsulating the roof.

However, the technical installations were to be completely replaced with the LowEx components developed by the professor. “Our focus was on the building systems – in other words, the heating, ventilation and lighting installations” , says Philippe Goffin, explaining the key aspects of the renovation strategy, which was designed to be economically efficient. “We wanted to test out whether buildings, which were poorly insulated originally, could be adapted to meet today’s high energy efficiency standards without any costly total reconstructions.” These standards have now been met.

Keeping temperatures at a comfortable level

The building is now heated and cooled by a decentralised system of ceiling panels, which can be individually controlled as required. One of the many advantages of this low-temperature-based system is that it only needs supply temperatures of up to 32ºC for heating, compared to the temperatures of 60ºC or more required before the renovation. On top of this, two exhaust air heat pumps recover and reuse waste heat during the winter, while the need for air conditioning in the summer is reduced thanks to the highly effective solar control glazing (M-glass) installed throughout the building. M-glass filters infrared and UV rays out of the light spectrum, letting plenty of daylight into the interior but only a small amount of heat.

The new insulation added to the roof also helps to reduce the need for heating and cooling. Another energy-efficient feature is the Airbox mechanical air supply units, which have been fitted in every office to heat or cool fresh air as required before it is circulated. The air is extracted via the ceiling panels in a CO2-controlled ventilation system, which reduces the air exchange rate and thus keeps temperature loss to a minimum.

“The energy required for the building is supplied by the campus’ energy supply network, known as the ‘Anergy Grid’, and generated by a central heat pump,” explains Philippe Goffin when questioned on the subject. Spring 2012 saw the first office buildings connected to this new, dynamic geothermal heating system on the Hönggerberg campus which stores excess heat generated from cooling in the summer and uses it for heating in the winter. The campus-wide Anergy Grid links the individual buildings and geothermal probe fields in a network.

The intention is for the buildings on this campus to be heated and cooled with virtually zero emissions by 2025. The high demands set by such an extensive geothermal heating system in terms of regulating heating, air conditioning and ventilation systems are clear to see, which makes the success achieved by the engineers at the Institute of Technology in Architecture seem even more impressive: thanks to the newly developed installations, the LowEx building system concept implemented in the former physics building was able to meet these demands, marking an important step in the advancement of environmentally friendly building systems.